The parenteral route is preferred over oral ones in many occurrences. For example, when the drug to be administered would partially or totally degrade in the gastrointestinal tract, parenteral administration is preferred. Similarly, where there is need for rapid response in emergency cases, parenteral administration is usually preferred over oral.
Thus, while parenteral administration is desirable in many applications, as it is currently practiced, it presents substantial drawbacks. Probably the biggest drawback is the discomfort which it causes the patient to whom the drug is being administered. Parenteral preparations generally contain a large volume of liquid in which the drug is suspended or dissolved. Ratios of active ingredient to carrier commonly run from 1:100 to 1:1000. Especially where the active ingredient is poorly soluble or difficult to suspend, or when it has to be administered at high doses, or in both instances, a fairly large volume of liquid must be injected. The injection of the needle and the introduction of a fairly large volume of liquid cause parenteral administration to be more or less painful and at least disagreeable, for most people. Furthermore, depending on its nature, the solvent or the suspending agent may itself be a cause of pain.
A further disadvantage to administration of drugs in a liquid carrier is that the drugs are frequently not stable in the liquid. Therefore, the liquid and drug must be mixed substantially contemporaneously with injection. This can be of substantial disadvantage where, for example, many hundreds of people must be treated over a course of days in order to stem an epidemic.
Accordingly, it would be interesting to find a mode of administration avoiding the use both of a needle and of a liquid solution or suspension.
Parenterally administered solid compositions for use in the controlled release of a medicament are known and devices allowing direct injection of a medicament without need of a liquid are known such as, for example, trocars for implants of rods or pellets, and the device shown in European Patent Application No. 0292936 A3 for injection of a solid. However, trocars and the device of European Patent Application No. 0292936 A3 still require use of a needle.